1. Field of the Invention
The present invention relates to a volume hologram laminate which can reduce spotty hologram flaws produced by stacking or by storage under pressure during transport or warehousing, and to a label for fabrication of a volume hologram laminate.
2. Description of the Related Art
Volume hologram laminates developed in the past have generally had a construction wherein an adhesive layer, a volume hologram layer, an adhesive layer and a transparent protective film are laminated in that order on a substrate, the substrate for the adhesion being of various forms such as examination admission tickets, ID cards, small booklets such as passports and so forth; however, in the case of dry volume phase-type hologram recording materials wherein the hologram recording material is a recording material comprising a matrix polymer and a photopolymerizable compound, a problem is presented by spotty hologram flaws which occur during stacking for transport or warehousing or storage under a state of pressure, as in the case of books, for example.
Such spotty hologram flaws become apparent by observing the hologram recording layer, and the spots are oval-shaped with a long axis of 0.2-2 mm and a short axis of 0.1-1.5 mm, approximately, or circular with a radius of about 0.1-2 mm, occurring in a regular arrangement. Because this type of hologram flaw depends on the light source and the angle from which it is viewed, it can be considered a holographic flaw instead of contamination by air bubbles or foreign matter in the volume hologram layer.
It is an object of the present invention to provide a volume hologram laminate free of such hologram flaws and a label for fabrication of the volume hologram laminate, and it is a further object to provide a volume hologram laminate with low occurrence of spotty hologram flaws in the volume hologram layer even when kept under a state of pressure during storage, etc., as well as a label for fabrication of the volume hologram laminate.
First Invention
The first invention includes the following aspects. The volume hologram laminate according to the first aspect is a volume hologram laminate having a first adhesive layer, a volume hologram layer, a second adhesive layer and a surface protective film formed in that order on a substrate, characterized in that the volume hologram layer is a hologram recording in a recording material comprising a matrix polymer and a photopolymerizable compound, having a glass transition point of 30xc2x0 C.-70xc2x0 C. and a dynamic storage elastic modulus of 5xc3x97105 Pa-5xc3x97107 Pa at 50xc2x0 C. when measured at 6.28 rad/s, and the second adhesive layer has a dynamic storage elastic modulus of no greater than 5xc3x97104 Pa or at least 2.5xc3x97105 Pa at 50xc2x0 C. when measured at 6.28 rad/s.
The volume hologram laminate-fabricating label according to the second aspect of the invention is characterized in that a first adhesive layer, a volume hologram layer, a second adhesive layer and a surface protective film are formed in that order on a peel sheet, the volume hologram layer is a hologram recording in a recording material comprising a matrix polymer and a photopolymerizable compound, having a glass transition point of 30xc2x0 C.-70xc2x0 C. and a dynamic storage elastic modulus of 5xc3x97104 Pa-5xc3x97107 Pa at 50xc2x0 C. when measured at 6.28 rad/s, and the second adhesive layer has a dynamic storage elastic modulus of no greater than 5xc3x97104 Pa or at least 2.5xc3x97105 Pa at 50xc2x0 C. when measured at 6.28 rad/s.
It is preferred for the half-width of diffraction light (half-bandwidth of diffraction light) in a volume hologram recorded in the volume hologram layer of the volume hologram laminate or volume hologram laminate-fabricating label to be no greater than 30 nm.
The present invention has been completed upon determining that hologram flaws in volume hologram laminates are generated substrated on a correlation between the hardness of the volume hologram layer and the hardness of the adhesive layer formed between the volume hologram layer and the surface protective film.
Second Invention
The second invention includes the following aspects. The volume hologram laminate according to the first aspect is a volume hologram laminate having a first adhesive layer, a volume hologram layer, a second adhesive layer and a surface protective film formed in that order on a substrate, characterized in that the volume hologram layer is a hologram recording in a recording material comprising a matrix polymer and a photopolymerizable compound, having a glass transition point of 30xc2x0 C.-70xc2x0 C. and a dynamic storage elastic modulus of 5xc3x97105 Pa-5xc3x97107 Pa at 50xc2x0 C. when measured at 6.28 rad/s, and the second adhesive layer has a loss tangent (tan xcex4), as represented by the dynamic loss elastic modulus/dynamic storage elastic modulus for the frequency dependent property at 10xe2x88x921 rad/s-10 rad/s, which increases with lower frequency.
The volume hologram laminate-fabricating label according to the second aspect of the invention is characterized in that a first adhesive layer, a volume hologram layer, a second adhesive layer and a surface protective film are formed in that order on the substrate, the volume hologram layer is a hologram recording in a recording material comprising a matrix polymer and a photopolymerizable compound, having a glass transition point of 30xc2x0 C.-70xc2x0 C. and a dynamic storage elastic modulus of 5xc3x97105 Pa-5xc3x97107 Pa at 50xc2x0 C. when measured at 6.28 rad/s, and the second adhesive layer has a loss tangent (tan xcex4), as represented by the dynamic loss elastic modulus/dynamic storage elastic modulus for the frequency dependent property at 10xe2x88x921 rad/s-10 rad/s, which increases with lower frequency.
It is preferred for the half-width of diffraction light in a volume hologram recorded in the volume hologram layer of the volume hologram laminate or volume hologram laminate-fabricating label to be no greater than 30 nm.
Third Invention
The third invention includes the following aspects. The volume hologram laminate according to the first aspect is a volume hologram laminate having a first adhesive layer, a volume hologram layer, a second adhesive layer and a surface protective film formed in that order on a substsrate, characterized in that the volume hologram layer is a hologram recording in a recording material comprising a matrix polymer and a photopolymerizable compound, having a glass transition point of 30xc2x0 C.-70xc2x0 C. and a dynamic storage elastic modulus of 5xc3x97105 Pa-5xc3x97107 Pa at 50xc2x0 C. when measured at 6.28 rad/s, and the second adhesive layer has a maximum logarithmic decrement of less than 1 or at least 2 according to surface viscoelastic measurement by a pendulum type rigidity test.
The volume hologram laminate-fabricating label according to the second aspect of the invention is characterized in that a first adhesive layer, a volume hologram layer, a second adhesive layer and a surface protective film are formed in that order on a peel sheet, the volume hologram layer is a hologram recording in a recording material comprising a matrix polymer and a photopolymerizable compound, having a glass transition point of 30xc2x0 C.-70xc2x0 C. and a dynamic storage elastic modulus of 5xc3x97105 Pa-5xc3x97107 Pa at 50xc2x0 C. when measured at 6.28 rad/s, and the second adhesive layer has a maximum logarithmic decrement of less than 1 or at least 2 according to surface viscoelastic measurement by a pendulum type rigidity test.
It is preferred for the half-width of diffraction light in the volume hologram recorded in the volume hologram layer of the volume hologram laminate or volume hologram laminate-fabricating label to be no greater than 30 nm.
The present invention has been completed upon determining that hologram flaws in volume hologram laminates are generated substrated on a correlation between the hardness of the volume hologram layer and the hardness of the adhesive layer formed between the volume hologram layer and the surface protective film.
Fourth Invention
The fourth invention relates to a volume-type hologram laminate characterized in that a transparent protective film is formed on the surface of a hologram layer via a transparent hot-melt adhesive layer.
The present invention has been completed upon determining that hologram flaws in volume-type hologram laminates are generated substrated on a correlation between the hardness of the volume-type hologram layer and the hardness of the adhesive layer formed between the volume-type hologram layer and the transparent protective film, and that such problems can be overcome by using as the adhesive a hot-melt adhesive which is solid up to a given temperature.